In general, human secretions such as sweat, tears and sebum spoil cosmetic materials. In particular, with suncut creams and makeup cosmetic materials, sebum secreted by the skin becomes mixed with cosmetic material blending oils, leading to excessive wetting of the cosmetic material which is a major factor causing it to deteriorate. To reduce the oils in the cosmetic material remaining on the skin, it has been attempted to use volatile oil agents such as octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane as a part of the oils which were blended.
Rubbing and water are external factors which spoil makeup. To improve poor makeup lasting properties which occur due to water-soluble substances, such as sweat and tears, to prevent loss of aqueous components or sebum in the skin and to maintain skin protection, silicone oils are blended to improve water repellence. For example, due to their light feel, outstanding water-repellence and high safety, silicone oils such as dimethylpolysiloxane have been used abundantly as oils in cosmetic materials in recent years. At the same time, powders, e.g., pigments such as titanium oxide, zinc oxide, red ocher, mica and sericite are widely used in basic cosmetics, suncut materials, nail colors and nail coats, foundation, mascara and eyeliner. To block the surface activity of these powders and impart water resistance and sebum resistance, it is common to give them a surface treatment such as alumina treatment, silica treatment, oil treatment, metallic soap treatment or organopolysiloxane treatment.
In recent years, in many cases, the organopolysiloxane has a reactive part within the molecule. The organopolysiloxane forms a chemical bond with the powder, which modifies the powder surface and blocks its surface activity. Also, the treatment agent does not secede from the powder surface even if a solvent system cosmetic material is used, and as change of cosmetic material properties due to treatment can be reduced, this is highly effective.
For example, in Japanese Patent (JP-B) No. 2719303, a method of carrying out the surface treatment by 12-60 wt parts of methylhydrogen polysiloxane to 100 wt parts of powder, is disclosed. In Japanese Unexamined Patent Publication (JP-A) No. 07-196946, a surface treatment method which uses a straight chain single terminal alkoxy-modified silicone is disclosed. Thus, powder treatment by a reactive organopolysiloxane is a generally known technique, however in all cases, the blocking of the powder surface activity was insufficient, and in particular, when the treatment agent was a methylhydrogenpolysiloxane (methyl hydrogen polysiloxane or dimethylhydrogenpolysiloxane), as unreacted Si—H groups remained in the powder even after surface treatment when the powder was blended with the cosmetic material, there was a problem of hydrogen gas being generated depending on the condition of liquid properties of the cosmetic material. Moreover, when a powder treated with a single terminal alkoxy-modified silicone was used as a pressed powder cosmetic material, there were few problems regarding water resistance and sebum resistance, but when it was used in a solution system, the treatment effect could not be said to be adequate. This is considered to be due to few reactive sites which react with the powder as compared with a methylhydrogen polysiloxane treatment agent, so that untreated parts remain in the powder surface.
Thus, although conventional powders treated by reactive organopolysiloxane treatment agents had outstanding aspects, they were not effective in all forms of cosmetic materials. A surface-treated powder with improved blocking of surface activity, water resistance and sebum resistance was therefore desired.
As a result of intensive studies carried out to discover a surface-treated powder with improved blocking of surface activity, water resistance and sebum resistance, the Inventors found that by surface-treating the powder with an acrylic/silicone copolymer having at least one hydrolyzable silyl group in the molecule, a good surface-treated powder can be obtained, and by blending this surface-treated powder with a cosmetic material, a cosmetic material which was very pleasant to use, long-lasting and very stable over time was obtained, and thereby arrived at the present invention.
It is therefore a first object of the invention to provide a surface-treated powder having an improved surface treatment (blocking of surface activity, water resistance and sebum resistance).
It is a second object of the invention to provide a cosmetic material which is very pleasant to use, long-lasting and very stable over time.